post-review proto version
Merged revisions 44396,44404 via svnmerge from 
https://svn.boost.org/svn/boost/trunk

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  r44396 | rogeeff | 2008-04-13 22:51:49 -0700 (Sun, 13 Apr 2008) | 2 lines
  
  initiaize stack_t structure with nulls, before calling sigaltstack
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  r44404 | emildotchevski | 2008-04-13 23:27:40 -0700 (Sun, 13 Apr 2008) | 1 line
  
  minor fix
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